Sansui established this long time ago officially ending successfully with their project to create a S.S. design that will sound exactly as their top amplifier AU111...
Then from this came half of your sentence : some tube designer effectively created S.S. design sounding exactly as tube design... ... Effectively the tube and transformer designer Sansui going S.S. design create two amplifiers sounding exactly the same, one was tube and the other S.S. ...
The other half of your sentence about the fact that no manufacturer never said that their tubes amplifier sound like S.S. design is not exact... David Berning said so and he is one of the best tube designer in the world...he claim that his tube design sound fluid as tubes and detailed and dynamic as S.S. design...
Some tube manufacturer claimed exactly that as Berning did because S. S. design has also his qualities , faster dynamic, more details, more power etc
Then your sentence is not a very deep truth but a common place joke born from design prejudices...
The reality is any design is a trade-off master piece or not , being tubes or S. S. ; but some company succeed better than others, being S. S. or tubes...
😊
Ever notice that SS manufacturers and merchants often tell us their device ’sounds like tubes’ but no tube manufacturer sez their device sounds like SS. :-)